The present invention relates to a sheet transport apparatus mounted on an image reading apparatus such as a facsimile machine and digital copier, or an image forming apparatus (hereinafter referred to as a sheet processing apparatus) that forms images on sheets (for example paper, film sheets or Mylar sheets). The sheet transport apparatus transports sheets stacked on a paper feed stacker to an image reading unit of the image reading apparatus or an image forming unit (hereinafter referred to as a processing unit) of the image forming apparatus, and discharges the processed sheets to a discharge stacker.
In general, a sheet processing apparatus is provided with a sheet transport apparatus having a paper feed stacker for stacking sheets and a discharge stacker for discharging the sheets as disclosed in, for example, Japanese Patent Publication No. 2002-173243. Transport means is provided between the paper feed stacker and discharge stacker for transporting the sheets from the paper feed stacker to the discharge stacker. Reading means is provided under a platen for reading an image on the sheet when the sheet is drawn out from the paper feed stacker and passes over the platen (sheet-through reading method). The paper feed stacker and discharge stacker are arranged adjacent to each other in the vertical direction for space conservation.
After the sheet is drawn out from the paper feed stacker and processed, the sheet is discharged consecutively to the discharge stacker by a pair of discharge rollers. In this case, it is preferred that the sheet is discharged in order with good alignment so that it is easy to align the sheets after being discharged. To this end, Japanese Patent Publication (Kokai) No. 05-338926 has disclosed a sheet controlling member integrally formed of a feed control unit for controlling a width direction of a sheet stacked on a paper feed stacker and a discharge control unit for controlling a width direction of a sheet discharged to a discharge stacker. The feed control unit has a pair of guide plates contacting both sides of the stacked sheet and being separated through an interlocking mechanism. The discharge control unit has substantially U-shaped side plates integrated with the pair of the guide plates. Also, the side plates of the discharge control unit are provided with widening portions at front edges thereof to control the sheet even when the sheet is discharged with a skew after being processed.
In the configuration disclosed in Japanese Patent Publication (Kokai) No. 05-338926, after the sheet is processed, the sheet is sequentially discharged between the pair of the side plates with a substantially U shape. The side plates only slide in the width direction along with the pair of the guide plates of the feed control unit to control the width of the sheet to be processed. Accordingly, when an operator takes out the sheet stacked on the discharge stacker, the operator needs to pull out the sheet in a direction same as that the sheet is discharged, thereby causing a problem in workability. Also, in order to remove the sheet in the direction same as that the sheet is discharged, it is necessary to provide an enough space in the discharge direction for the operation.
Also, when the processed sheet is discharged with a skew, the sheet abuts against the widening portion to be guided between the pair of the side plates. At this time, the sheet edge tends to crinkle or bend.
In view of the problems described above, the present invention has been made. A first object of the present invention is to provide a sheet transport apparatus that can align and order sheets discharged on a discharge stacker after being processed at a processing unit, in which it is easy to remove the stacked sheets with a limited space. A second object of the present invention is to provide a sheet transport apparatus that does not damage the discharged sheets.
Further objects and advantages of the invention will be apparent from the following description of the invention.